Use a locknut over or in place of a regular nut to resist loosening due to machine vibration or torque. There are two main types of lock nut. A nylon insert nut has a slightly smaller thread than the bolt to provide added grip. It is reusable but not recommended for high-temperature applications. A deformed thread locknut, as the name implies, has a distorted thread for added friction. Lock flange nuts have a toothed washer on the bottom for grip. Grainger has a large locknut selection to keep your machinery running at top efficiency.